The microbiological quality of 745 conventionally processed and 745 reprocessed broiler carcasses was determined. Carcasses were taken from the processing line prior to entering the chiller in five commercial processing plants. Each plant was sampled twice during the winter, spring, and summer. Analyses included aerobic bacteria, Enterobacteriaceae , and Escherichia coli counts plus qualitative Salmonella (SAL) prevalence. Differences between overall mean log 10 counts for aerobic bacteria, Enterobacteriaceae , and E. coli were not significant. The prevalence of SAL detected on conventionally processed and reprocessed carcasses also was not significantly different. Some variation was observed in microbiological quality of carcasses among processing plants. Although the SAL prevalence appeared to decline from winter to summer replications, no significant trend could be demonstrated. Continuation of the practice of reprocessing carcasses appears justified.

Two hundred and twenty-five pork carcasses were sampled immediately after slaughter and 24 h postmortem for the presence of Campylobacter spp. and Salmonella spp, Campylobacter spp. were present on 23 carcasses with 9 isolates from the shoulder area and 14 isolates from the ham. Salmonella spp. were isolated from 63 carcasses with 29 isolates from the shoulder and 34 isolates from the ham area. Spraying with a 2% solution of lactic acid reduced the numbers of both organisms that could be isolated immediately and 24 h after slaughter from the 75 carcasses sprayed. All of the Campylobacter spp. isolated in this study were confirmed to be Campylobacter coli .

Three hundred and ninety raw processed broiler carcasses were obtained from four processing plants and evaluated for the presence of salmonellae by the whole bird rinse procedure. Enzyme immunoassay (Salmonella-Tek ™ ), colorimetric DNA hybridization (GENE-TRAK R ), and antibody immobilization (1–2 Test ™ ) methods were compared to the Food Safety Inspection Service (FSIS) culture method for detection of salmonellae. All samples were preenriched in buffered peptone water incubated at 37°C then transferred to and enriched in TT broth (Difco, Detroit, MI) incubated at 42°C for 24 h. After enrichment, manufacturer's instructions were then followed for “rapid” procedures and the FSIS recovery and confirmation scheme was followed for the cultural method. For each sample, if discrepant results were observed between the four procedures, selective plates were streaked from both the TT selective broth and the GN postenrichment broth (Difco). All samples which were positive after initial sampling of TT broth plus additional positive samples from TT selective and GN postenrichment broths were called confirmed cultural positives. Salmonellae were detected on 71% of the carcasses using confirmed cultural procedures and 65% with FSIS culture. Presumptive salmonellae positive samples were found 66, 71, and 76% of the time with the 1–2 Test, GENE-TRAK, and Salmonella-Tek, respectively. As compared to confirmed culture, only 1.4% false positives were observed with the 1–2 Test and GENE-TRAK, whereas 6% false positives were obtained using Salmonella-Tek. When the false negatives for the four methods were compared to confirmed culture, Salmonella-Tek, GENE-TRAK, 1–2 Test, and FSIS culture had 0.4, 2.5, 7.2, and 8.3%, respectively. The close correlation of these rapid procedures to the conventional procedures warrants consideration of these procedures for detection of salmonellae from broiler chickens.

Title 9 of the Code of Federal Regulations establishes prescribed thermal treatment for a variety of meat and poultry products. These requirements are to ensure the destruction of harmful microorganisms and viruses that cause diseases in humans and livestock. The information presented in this review provides information relative to the current procedures used by the Food Safety and Inspection Service (FSIS) for monitoring the adequacy of heat treatment of meat and poultry products; and the research activities that have been and are currently being conducted to develop new and/or improved methods for determining the maximum internal temperature of meat and poultry products. Currently, FSIS is using a protein “Coagulation Test” for monitoring the maximum internal temperature (MIT) of both beef and pork products heat processed to temperatures lower than 65°C; a residual “Acid Phosphatase Activity Method” for determining the MIT of canned hams, canned picnics and canned luncheon meat, and a third method, known as the “Bovine Catalase Test”, for the determination of catalase which gives a pass/fail indication at a cooking temperature of 62.8°C for rare roast beef and cooked beef. Since 1957, several attempts have been made to develop new and/or improved methods. These include an evaluation of the enzyme systems and various physical techniques. The lack of new and/or improved methods is not due to the lack of research efforts in this area, as evidenced by this review. The challenge is the development of a method which can accurately determine within ± 1.0°C the endpoint temperature in the temperature range (67.8 – 70.0°C) that is of most interest to FSIS.

Muscle pyruvate kinase (PYK) activity was established as a biochemical indicator of temperature attained during cooking in both a model system and a commercial-type pullman-style canned cured pork product. Water extract (model system) or pressed-out meat juice (commercial-type pullman-style canned cured pork) was incubated (37°C up to 40 min) with reagent containing adenosine diphosphate, phosphoenolpyruvic acid and NADH. Lactate dehydrogenase (LDH) necessary for the reaction is provided by the muscle extract or meat juice. When muscle PYK activity is present, NADH is oxidized resulting in a loss of fluorescence (reaction mixture spots on filter paper viewed under long-wave ultraviolet light). Model system results showed high PYK activity (no fluorescence) remained in samples heated to 67.7°C. PYK activity progressively declined in samples heated to 68.3°C and 68.9°C. No PYK activity was detected in samples heated to 69.5°C or 70°C. Canned product attaining a core temperature of 62.9°C had high PYK activity. PYK activity progressively declined in product heated to 65.6°C and 68.6°C. Essentially no PYK activity was detected from product processed to 69.9°C.

Reductions in the levels and incidence of salmonellae in poultry scald water by the addition of acetic acid have been reported previously. Hence, acid treatment of scald water may help control cross-contamination of carcasses in the scald tank. However, the effect of acid-treated scald water on microbial levels of scalded carcasses has not been addressed. This study confirmed reductions in levels of total aerobic bacteria and Enterobacteriaceae in scald water containing 0.2 and 0.5% acetic acid; salmonellae were not detected. No significant reductions occurred in levels and/or incidence of salmonellae, total aerobic bacteria and Enterobacteriaceae on unpicked carcasses sampled after scalding in 0.5% acetic acid-treated scald water or on picked carcasses that were acid scalded and sprayed with 0.5% acetic acid water during picking.

Samples of fresh pork skin were inoculated with known numbers of a nalidixic acid-resistant strain of Campylobacter jejuni and sampled by two methods, swabbing and scraping, 10 min after inoculation to compare sampling methods. The effect of frozen storage of samples on detection was also examined. C. jejuni was readily recovered with swab samples while recovery of the organism was greatly reduced by the scrape method. Frozen storage of samples decreased the numbers of viable cells as compared to the fresh samples.

Pork skin inoculated with a nalidixic acid-resistant strain of Campylobacter jejuni was subjected to three treatments to determine the effect of storage temperature, oxygen concentration, and drying on survival of the organism. Survival rate was determined for each treatment by enumeration over a 48-h period on Brucella agar containing nalidixic acid. Of the treatments studied, chilling with forced ventilation and storage at 20°C caused significant reductions in numbers of survivors. The results of this study confirm reports by other investigators that conventional forced ventilation chilling of pork carcasses has the beneficial effect of reducing skin surface Campylobacter contaminants.

One hundred and twelve freshly slaughtered pork carcasses from three packing plants were sampled before and after chilling for the presence of Campylobacter jejuni / coli by the use of two isolation methods (Preston enrichment and Skirrow direct plating). Preston enrichment media gave the highest isolation rate, 12.5%, on freshly slaughtered carcasses. No isolations were obtained from chilled carcasses. More isolates were obtained from the ham skin area compared with the jowl area. All isolates were confirmed as Campylobacter coli .

Swab, rinse and excision sampling methods are commonly used for detection of microorganisms on poultry carcasses. Swabbing has been the most frequently reported sampling method for Campylobacter jejuni on poultry. We evaluated the three methods for C. jejuni detection on freshly processed poultry in the following ways: (a) the interior and exterior surfaces of half of a carcass were each thoroughly rubbed with separate swabs which were combined in a test tube containing 2 ml of appropriate medium; (b) 25 g of skin and tissue samples from neck and abdominal opening cut areas were deposited in a stomacher bag with 5 ml of brucella broth (BB) and stomached for 2 min; and (c) half carcasses were shaken for 1 min with 100 ml BB in plastic bags. One drop of each sample was streaked for isolation on brucella agar containing 10% defibrinated sheep blood and Skirrow antibiotics. Isolates were identified by microscopy and appropriate cultural tests. All three sampling techniques were essentially equivalent for detection of C. jejuni on fresh carcasses. However, when samples were stored frozen for 7 to 10 d to simulate transport conditions from sampling locations to the laboratory, the incidence of detection was significantly reduced. Use of cryoprotective agents was an effective method to preserve swab samples during frozen storage.

Raw beef inoculated with cells of a composite of five Salmonella strains was heated at 54 or 60°C. Survivors were enumerated by plating samples in plate count agar (PCA), XL agar or PCA followed by an XL agar overlay. Best differential recoveries of salmonellae were effected by incubation of PCA plates for 4 h at 37°C followed by overlay with XL agar and incubation for an additional 44 h. D-values of salmonellae at 54 and 60°C were increased significantly when ground beef was supplemented with 30% textured soy protein, soy protein concentrate or isolated soy protein. Increased heat resistance appeared to be caused by an increase in the pH of beef from 5.8–5.9 to 6.1 upon addition of the soy proteins. After adjusting the pH of mixtures of beef and soy proteins with hydrochloric or lactic acid to 5.8 to 5.9, survival of salmonellae to heat was reduced to the level of survival in beef alone. The pH of beef with added structured soy isolate was the same as beef, and heat resistance of salmonellae was not increased in this product. In the pH range 5.9 to 7.1, the maximum heat resistance of salmonellae in beef containing textured soy protein occurred at pH values of 6.5 to 6.8.

The injury and recovery characteristics of Salmonella bareilly after treatment with acetic acid in saline solution containing 0.5% sucrose were studied. Injury and death rates were dependent upon acid concentration and temperature. Several enzyme activities were substantially reduced in injured cells. Recovery rates were greater in peptones and casamino acids than in several commonly used culture media. The effects of a variety of inhibitors and antimetabolites on recovery of acid-injured cells indicated that protein and RNA synthesis, as well as electron transport, were necessary for recovery.

The effect of three commercial soy proteins on growth and production of enterotoxin by Staphylococcus aureus S-6 was determined. Sterile isolated soy protein (ISP), soy protein concentrate (SPC), and textured soy protein (TSP) were adjusted to 20% protein by diluting with sterile nutrient medium, inoculated with S. aureus S-6 and incubated at 37 C. Generation times of S. aureus S-6 in ISP, SPC, and TSP were 41, 38, and 33 min, respectively. At 48 h, log 8.4 – 8.5 organisms/g were found in the soy products, and staphylococcal enterotoxin A (SEA) and staphylococcal enterotoxin B (SEB) were produced. Each of three hydrated soy protein products was added to ground beef or pork sausage to attain 20% (wt/wt) and cooked to 71 C. Each product was then inoculated and incubated at 37 C. Generation times of S. aureus S-6 did not differ significantly for any beef-soy or pork-soy samples compared to beef or pork sausage controls. Production of SEB (12–72 h) was similar in most beef-soy and pork-soy samples compared to controls, but was significantly lower in the beef-SPC product and beef-TSP and significantly higher in pork-ISP. Small quantities of SEA were produced in beef, beef-soy, pork, and pork-soy samples. Possibly reduction of enterotoxin production in some meat-soy samples was due to outgrowth and competition by spore contaminants of the soy proteins that survived cooking. Production of SEB in all beef-soy and beef control samples was not significantly different when raw samples were autoclaved before inoculation.

Non-destructive, whole carcass, water rinse sampling followed by addition of sterile, dry lactose broth for pre-enrichment is shown to be a sensitive method for detection of small numbers of salmonellae on experimentally contaminated eviscerated broiler chicken carcasses.

Pure cultures of yeast, molds, and bacteria were screened for neutral pH optimum β -galactosidases (lactases) that would be suitable in dairy products applications. Only 2 of 125 identified and 10 of 250 unidentified cultures warranted further study. These cultures produced high levels of β -galactosidase with moderate galactose product inhibition. Characterization of the partially purified enzymes from unidentified cultures revealed that all required either Na + , K + or Mg ++ cation activation, were inhibited by Cu + + , Mn + + , and Fe + + + , were most active around pH 6.8, and were unstable during storage (at either – 196 C or 4 C) except in the presence of 0.5 m ammonium sulfate. Most of the enzymes compared favorably in performance with a commercially available β -galactosidase when tested in skim milk.